Dyeing cellulose esters



Patented Feb. 23, 1954 DYE-ING CELLULOSE ESTERS Richard Wilson Nebel, Chester, Va., assignorto E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application August 31, 1951, Serial No. 244,741

3 Claims.

This invention relates to the dyeing of cellulose acetate and more particularly to the dyeing of textile materials made from modified cellulose acetate.

A commercial process for obtaining vat dyed cellulose acetate textile materials has long been desired. The methods in the prior art involve complicated or costly procedures or result in degradation of the cellulose acetate textile material. Such methods include the use of organic solvents as swelling agents, various ways of reducing the alkalinity of the dyebath containing the leuco form of the vat dye, the use of colloidal materials such as glue and other albuminous substances as protective agents to reduce the saponification of the cellulose acetate and the isolation of the free leuco form of the vat dye for subsequent dyeing in neutral or acidic media. These methods are not of commercial interest.

It is an object of this invention to provide a process for obtaining cellulose acetate textile materials dyed with vat dyes. It is a further object to make available a commercially feasible method for vat dyeing cellulose acetate fibers, films, fabrics, and the like. Other objects appear hereinafter.

These objects are accomplished by modifying articles made from cellulose acetates with polymeric amino alcohol esters of acrylic acid or of alpha-substituted acrylic acids, placing the modified cellulose acetate in a bath containing'a salt 30 minutes, withoccasional turning of the fabric.

The fully oxidized sample, now a bright pink, is rinsed in cold water, neutralized for five minutes in a cold solution containing two grams per liter of sodium carbonate, and then soaped for 15 minutes at 80435? C. with two per cent green soap, rinsed and dried.

The resulting dyeing is of astrong shade of pink representing essentially complete exhaustion of the dye bath, and having 20-40 hours Fade-Ometer fastness, and high fastness to fumes, crocking and washing.

EXAMPLE II An aqueous dye bath is prepared containing 15 per cent sodium sulfoxylate formaldehyde, four of an acid ester of a leuco vat dye and following 1 the impregnation by rinsing, oxidizingthe leuco dye, neutralizing, scouring and drying. The process of this invention is economical; it does not involve adverse polymer degradation; and, further, it is commercially acceptable. The poly- Ineric alcohol esters dissolve readily in the solvent for the ester being modified, and the resultant blend is readily dyed by the process of this invention, either as a mere blend or as a shaped article. I n w The following examples serve to illustrate the process of this invention but it is not intended that these examples, in any way, limit the scope of this invention.

EXAMPLE I An aqueous dye bath is made up containing five per cent of sodium sulfoxylate formaldehyde, three per cent of Indigosol Pink IR and ten per cent glacial acetic acid in a 40:1 liquor volume to fabric ratio. Cellulose acetate knitted fabric, prepared from yarns modified with five per-cent of polydimethylaminoethylmethacrylate, previously wet out, is entered in the bathat room -temper cent of Indigosol Green IB paste, two per cent of Indigosol 0413 (Blue) and 15 per cent of glacial acetic acid in a 40:1 liquor volume to fabric weight ratio. Cellulose acetate knitted fabric, prepared from yarns modified with seven per cent of polydimethylaminoethylmethacrylate, previously. wet out, is entered in the bath at room temperature. The bath temperature is raised to 70 C. over a 15-minute period, and maintained at this temperature for minutes, while working the fabric in the bath. The fabric is then rinsed in cold water and developed in a solution containing three per cent sodium nitrite and five grams per liter of sulfuric acid. The fabric is entered in the developing bath at room temperature and then heated to 80 C. for 20 minutes. Rinsing, neutralizing, and..soaping are carried out out as described in Exarnple I.

The resulting dyeing is a heavy shade of green, which has better than. 80 hours lightfastness, and

' which is fast to fumes, crocking, and washing at perature. The fabric is worked continuously in this bath while the temperature is raised as rapthe boil.

EXAMPLE III The aqueous dye bath is prepared containing one per cent of Indigosol 04B (Blue), five per cent anhydrous sodium sulfate, and live per cent of glacial acetic acid, in a 40:1 bath-to-fiber ratio. Cellulose acetate knitted fabric, containingjfive per cent of 'polydiethylamino'ethylmethacrylate, is wet out and entered. in the cold dye bath. The fabric is worked in the dye bath while the tem- 3 perature is raised to 80 C. over a -minute period. Dyeing is continued for minutes, five per cent of glacial acetic acid is added, and heating is continued at 80 C. for another minutes. To the dye bath is added two per cent potassium dichromate and 25 per cent of sulfuric acid. The oxidation is carried out at 80 C. for 20 minutes, after which time the fabric is removed from the bath, rinsed, neutralized, and soaped'as described in Example I.

The dyeing so obtained is a strong blue, representing essentially complete exhaustion of the dyestuif on the fiber, and being fast to light, fumes, crocking, and scouring at the boil.

The above described procedures are generally applicable to most of the available solubilized vat colors. Dyeings may be carried out with the addition of selected surface-active agents to im prove penetration, or to decrease the strong affinity of the dye for the fiber. The length of time of immersion and the bath temperature will, of course, depend upon the result desired and conventional times and temperatures are generally used. Similarly, many other oxidizing procedures are equally-satisfactory and these include the use of such agents as chromic acid, metallic chlorates and ferric chloride. With dyestufis of this class which are sensitive to over oxidation, the addition of a stabilizer such as ammonium sulfocyanate to the developing bath may be advisable.

In Tables 1 and 2 below, are listed the names of the dyes (together with their chemical constitution) which have been used according to the examples given above. In Table 1 arelisted representative dyes which are essentially exhausted from the dye bath by fabrics containing 5 per cent polydimethylaminoethylmethacrylate. dyestufis listed in Table 2 dye these modified yarns to deep shades but do not exhaust the dye bath completely under the described conditions. However, the dyes in Table 1 and Table 2 are The equivalents in all other respects. It is well-known that the efiiciency of dye bath exhaustion varies from dye to dye and of course depends upon the concentration of the modifier in the cellulose acetate textile material. The difference is pointed out merely to assist the trade in the selection of a dye to fit the needs.

Indigosol Bz'iiliunt Pink 15B. Indigosol 0413 (Blue) Indigosol (16B (Blue) Indigosol Red Violet IRE";

6,6-Dichloro 4 4 dimet'nyl 2,2-

bis-thionapbt :enindigo.

Halogenated thioindigo.

Tetrabromoindigo.

Hexabromoindigo.

5,5 Dichloro 7 7 dimethylthi oindigo.

Table 2 Name Constitution of the Parent Vat Dye Inldti glgsol Golden Yellow 33,8,9 -Dibenzpyrenquinone 5,10.

Indliagosol Golden Yellow I K Dibromo derivative of 3,4,8,9-Di- Indigosbl Scarlet IB benzpyrenquinone-5,l0. 6 Monoethoxv- 4, methyl 6 chlorothioindigo. Iudigosol Grey IBL Bcnzoxytbionaphthene indolindi- E Indigosol Green 13..-. Dim'ethoxydibenzanthrone. Indigosol" Brown IRRD Dibenzothloindigo.

Trade'nnme of Oarblc Color and Chemical Ink.

In Tables 1 and 2 above, it is to be noted that the chemical constitution of the various dyes has been given as that of the parent vat dye. A method of preparing (from those dyestuffs) the solubilized vat dyes of this invention is set forth below. Of course, after oxidation, the vat dye itself ends up within the modified celluulose textile fibers and accounts for the final color.

The fastness ratings of the dyeings have been determined according to the procedures described in the Technical Manual and Year Book of the American Association of Textile Chemists and Colorists, 1950 edition. The dyestuffs listed show a high order of light fastness (AATC'C Fade-Om- -eter Test 16-45), averaging 20 to 40 hours exposure, and in general these light fastness ratings thus approach those obtained with the same dyes on cotton or viscose rayon. These dyestufis on cellulose acetate modified as herein discussed are extremely fast to washing and show no color loss after minutes scouring at 82 C. with soap, chlorine and soda ash (AATCC Test 36-45, Wash Test No. 4'). In contrast, the large majority of dispersed color dyeings on the normal cellulose acetates of commerce, or for that matter on the modified cellulose acetates as herein described, show appreciable fading after 30 minutes washing with soap at 49 0., a much less severe washing test. The vat dyeings on modified cellulose acetate obtained by the process of this invention show an excellent fastness to rubbing (AATCC Test 8-45) and do not fume fade (a rating of 5 by the AA'ICC Test 23-46). In contrast, the dispersed colors on cellulose acetate particularly the blues and shades derived from them such as greens and grays, generally exhibit poor resistance to atmospheric fumes (an AATCC test rating of 1 to 2') It is to be understood that this invention is not restricted to dyeing modified cellulose acetate as hereinbefore described but encompasses the dyeing by this method of organic derivatives of cellulose in general which have been modified with a polymeric amino alcohol ester of acrylic acid or of alpha-substituted acrylic acids preferably where the range of modifier is 3 to 10%, based on the total weight of the textile material. Larger concentrations may be used if desired, however. A concentration of about 5% to about 7% is satisfactory for most purposes. The examples given above have been limited to cellulose acetate containing polydimethylaminomethylmethacrylate and polydiethylaminoethylpolymethacrylate with the former being the preferred modification. However, identical or similar workings of the examples using polydimethylaminoethylacrylate and polydimethylaminoethylacrylate also lead to the superior dyeings of this invention. Among the many cellulose esters which may be dyed by the process of this invention are cellulose propionate, cellulose acetate propionate, cellulose chloroacetate, cellulose butyrate, and cellulose acetate-butyrate.

While the polymeric amino alcohol esters of acrylic acid or of alpha-substituted acrylic acids of the type disclosed in U. S. 2,138,762 have been known and although U. S. Patent 2,168,338 mentions that an acetone solution containing 20% cellulose acetate and 4% of any of the said polymers can be dry spun into filaments which have a marked afi'inity for dyes, until the advent of the present invention, there was no commercially acceptable method for obtaining modified cellulose acetate textile materials dyed with vat dyes. The methods of the prior art did not involve the use of the acid esters of leuco vat dyes and depended upon swelling agents, protection agents and similar costly complications. The process of this invention avoids these undesirable costly procedures and makes available for the first time a commercial method-for vat dyeing cellulose esters.

The dyes which have been found to be unusually effective in producing extremely lightfast dyeings on modified cellulose acetate (described above) are either the full salts or the half salts of the acid esters of the leuco vat dyes. These may be produced, for example, by the action of pyridine-sulphur trioxjide or pyridinechlorosulfonic acid on the leuco form of any vat dye to form the disulphuric ester of the leuco vat dye which in turn is treated .with sufficient alkali to form either the full salt or the half salt of these two sulphuric ester groups. Esters other than sulfuric esters may be used; phosphoric esters may be used and them-sulfobenzoate ester is available. The sulfuric esters are usually used, for they are most readily available commercially. Likewise, salts other than sodium salts may be used, such as the potassium or ammonium salts. These dyes are soluble in water and are effectively applied to modified cellulose acetate textile materials from an acidic solution at normal dyeing temperatures and concentrations. The bath preferably should contain a reducing agent to keep the dye in the desired form. Since these dyes have affinity for the modified cellulose acetate, the color pick-up is rapid and even. Modified cellulose acetate textile materials thus dyed possess some minor utility, but the further treatment with an oxidizing agent in an acid solution produces the parent vat dye in situ in the fibers. Since the vat dyes are essentially water insoluble and are likewise very stable substances, the result is dyed textile materials of clear, bright shades which possess excellent wash fastness and light fastness and are resistant to fume fading and crocking.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the claims.

Iclaim:

1. A process for dyeing cellulose acetate which comprises blending said cellulose acetate with from about 3% to about 10%, based on the weight of the said cellulose acetate, of a member of the class consisting of polydimethylaminoethylmethacrylate and polydiethylaminoethylmethacrylate; impregnating the resultant blend with a. sodium salt of the sulfuric ester of the leuco form of the dye, 6,6'-dichloro-4,4'- dimethyl 2,2 bis thionaphthenindigo; rinsing the resultant impregnated material; and oxidizing the said dye.

2. A process for dyeing cellulose acetate which comprises blending said cellulose acetate with from about 3% to about 10%, based on the weight of the said cellulose acetate, of polydimethylaminoethylmethacrylate; impregnating the resultant blend with a sodium salt of the sulfuric ester of the leuco form of the dye, 6,6- dichloro 4,4 dimethyl 2,2 bis thionaphthenindigo; rinsing the resultant impregnated material; and oxidizing the said dye.

3. A process for dyeing cellulose acetate which comprises blending said cellulose acetate with from about 3% to about 10%, based on the weight of the said cellulose acetate, of polydiethylaminoethylmethacrylate; impregnating the resultant blend with a sodium salt of the sulfuric ester of the leuco form of the dye, 6,6'-dichloro- 4,4-dimethyl-2,2'-bis-thionaphthenindigo; rinsing the resultant impregnated material; and oxidizing the said dye.

RICHARD WILSON NEBEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,168,337 Heckert Aug. 8, 1939 2,376,891 Alles May 29, 1945 2,552,404 Casty May 8, 1951 OTHER REFERENCES Dyeing with Coal-Tar Dyestuffs, by C. M. Whittaker and C. C. Wilcock, published in London, 1942, by Balliere, Tindall and Cox, 4th edition, pages 28 to 31.

American Dyestufl Reporter for February 2-1, 1949, pages P172, P173. 

1. A PROCESS FOR DYEING CELLULOSE ACETATE WHICH COMPRISES BLENDING SAID CELLULOSE ACETATE WITH FROM ABOUT 3% TO ABOUT 10%, BASED ON THE WEIGHT OF THE SAID CELLULOSE ACETATE, OF A MEMBER OF THE CLASS CONSISTING OF POLYDIMETHYLAMINOETHYLMETHACRYLATE AND POLYDIETHYLAMINOETHYLMETHACRYLATE; IMPREGNATING THE RESULTANT BLEND WITH A SODIUM SALT OF THE SULFURIC ESTER OF THE LEUCO FORM OF THE DYE, 6,6''-DICHLORO-4,4''DIMETHYL-2,2'' - BIS - THIONAPHTHENINDIGO; RINSING THE RESULTANT IMPREGNATED MATERIAL; AND OXIDIZING THE SAID DYE. 